R&D Report 1954-40 : The Telefunken microphones Type Elam 200 and Elam 201.
W.I. Manson, D.E.L. Shorter, H.D. Harwood, J. Nash, R.J. Packer
Tests have been carried out on specimens of the Telefunken electrostatic microphones type ELAM 200 and ELAM 201. The ELAM 200 microphone is pressure-operated while the ELAM 201 can be switched to give either omnidirectional or cardioid characteristics; identical pre-amplifier arrangements are used for both types. The usual measurements of frequency response, sensitivity, impedance and susceptibility to magnetic fields were made and studio tests carried out.